A competitive Senate contest in the Hawkeye State is creating a ripple effect down ballot, causing headaches for national Democrats as Election Day nears.

Recentpollsshow state Sen. Joni Ernst, a Republican, with a small lead over Rep. Bruce Braley, a Democrat. But the Republican's advantage has percolated to three of Iowa's four House contests, keeping one competitive district in contention for Republicans, plus putting two Democratic seats in play .

In particular, Ernst's performance is buoying former Capitol Hill aide David Young, the Republican nominee in the competitive 3rd District, which is currently rated a Tossup by the Rothenberg Political Report/Roll Call. Privately, Iowa Republican operatives said Young is running a lackluster campaign against former state Sen. Staci Appel, a Democrat.

In the end, Ernst might be the one to pull him over the edge.

"I do think it looks to be like a pretty good year for Republicans in Iowa," said John Stineman, an Iowa Republican operative. "It’s kind of a nail biter, but both Young and Ernst should be able to pull this out if we keep the momentum."

Young raised $800,000 since unexpectedly emerging from a rare nominating convention in June, but his campaign was widely panned for a series of bizarre ads that lacked a clear message. At the end of September, Young pulled more than $100,000 worth of television ad time from the airwaves, leaving the National Republican Congressional Committee to pick up the slack. All the while, Appel ran on a message about being a mother of six who would work to protect education, while charging Young with wanting to eliminate the Department of Education.

Democrats have released a number of polls in the past few months that show Appel ahead. The most recent public survey conducted for the Democratic Congressional Campaign Committee showed Appel gaining significant ground.To the east, two more seats currently held by Democrats have become more competitive — a factor operatives also chalk up to Ernst's lead and Braley's underperformance. "All of that is being driven by the Senate race," said one Iowa Democratic operative, granted anonymity to speak candidly. "What’s going on there [in the House races] is an insurance piece."

Earlier this week, the Democratic Congressional Campaign Committee put out a $600,000 ad buy in the 1st District in the northeastern quadrant of Iowa.

Braley currently holds this seat, and President Barack Obama carried it by a 14-point margin in 2012. The open seat was considered safe for Democrats for most of the cycle, but polling suggests the contest is within striking distance for Republicans. On Friday, The Rothenberg Political Report/Roll Call changed its rating of the race to Tilts Democratic .

Businessman Rod Blum, the GOP nominee, has been attacking former state Speaker Pat Murphy on the airwaves in the 1st District.

The ad features Murphy in an angry tirade on the state House floor, and goes on to contrast Blum's ideas for the district. Iowa Republicans say it's an effective ad that, along with Braley's underwhelming performance, gives Blum a shot on Election Day.

Sensing opportunity and available airtime, other GOP outside groups are also getting involved.

American Action Network, an issue advocacy group with ties to House leadership, announced Friday it would spend $500,000 in the Cedar Rapids television market from Oct. 24 through Election Day to boost Blum.

There's another reason these races are in play: Cedar Rapids, which covers territory in the 1st and 2nd District, is one of the only markets left in Iowa with available airtime. The state's largest media market, Des Moines, is nearly sold out through Election Day. Also, unlike other markets, Cedar Rapids costs a more affordable $260,000 for a week's worth of ad time, according to a source tracking buys across the country. For example, it costs $1.4 million to run an ad for a week in Boston. It makes it easier for GOP outside groups to target a pair of House races in the final weeks.

To a lesser extent, top of the ticket headwinds are also helping Republicans in Iowa's 2nd District.